<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>分组选择器</title>
    <style>
        h1,h2,p{
            color: green;
        }
    </style>
</head>
<body>
    <h1>Hello World!</h1>
    <h2>Smaller heading!</h2>
    <p>This is a paragraph.</p>  
</body>
</html>